The present invention relates to an apparatus for electrical therapy for medical purposes, more particularly, to an apparatus for urinary incontinence treatment using an EMG (Electromyography) signal.
Urinary incontinence is a common problem throughout the world and is particularly prevalent in the female population and in the aged. A large number of women suffer from urinary incontinence due to childbirth or general deterioration of body structures as an aging process and so on. It is known that about 20-30% of women over 50 years old suffer from urinary incontinence. Resulting from urinary incontinence is embarrassment, discomfort and distress, loss of sleep and the necessity for large monetary disbursements by the patients for absorbent pads, diapers, rubber sheeting and for cleaning of soiled clothing.
These days the treatment for urinary incontinence includes surgery, physical rehabilitation and drug therapy.
The surgery treatment methods are invasive and thus most patients hesitate to choose this option over others. In addition, the drug therapies are known to provide very limited effectiveness. However, treatment for urinary incontinence is viewed differently by society as many non-invasive and non-pharmaceutical treatment methods are being introduced lately. Among such treatment methods, a biofeedback therapy and a neuromuscular electrical stimulation method are most commonly recognized as major treatment methods. These treatments have been proven very effective, safe to use and relatively inexpensive. In biofeedback therapy, repetitive contractions of pelvic floor muscles improve the strength of the pelvic floor muscles. Neuromuscular electrical stimulation method applies current pulses to pelvic floor muscles so that the motor nerve fibers are electrically stimulated. For more effective treatment for urinary incontinence, it is desirable that both biofeedback and neuromuscular electrical stimulation methods are performed at the same time, rather than one of them being independently performed.
For biofeedback treatment method for urinary incontinence, a patient follows pre-defined training courses to contract her pelvic floor muscles. At this time, it is very important to let the patient know how strong the pelvic floor muscles can contract according to her will.
This is because the effectiveness of the treatment increases along with the patient's positive attitude and willingness by objectively recognizing the improvement of the contractile force as the training progresses. In addition, doctors can create an effective training program in accordance with the observation of the training progress.
EMG signals are measured by the intensity of EMG proportional to the contractile force of the pelvic floor muscles. In doing so, one or more conductive electrodes are contacted with the surface of the vaginal wall. The electrode senses the voltage driven by the muscles, and the frequency of human EMG signals lies in the band between 20 and 800 Hz, which includes higher frequency components than other EMG signals.
FIG. 1 illustrates the typical waveform of such an EMG signal. However, such instantaneous transition of the EMG signals as seen in FIG. 1 is not required for analyzing the contractile force, but important is the overall transition of the amplitude of EMG signals as seen in FIG. 2, namely an envelope signal. Such an envelope of EMG signal has low frequency components, that is below 10 Hz.
However, the sampling frequency needs to be over 1,600 Hz in order to eliminate possible errors due to A/D conversion, because the raw EMG signal data contains high frequency components. However sampling using such a high frequency causes to complicate the structure of the device and raises the manufacturing cost.
In addition, the existing electrical therapy devices, such as urinary incontinence treatment devices, constipation/fecal incontinence treatment devices and low-frequency physical therapy devices, are very similar in their operating principles. Although, it is common to construct separate devices for each treatment purpose because each device has a unique form of electrode.